Device for amplifying and sampling multiplexed analog signals

Abstract

A device is provided for amplifying and sampling multiplexed analog signals so as to give them an optimum level before digitization thereof. It includes several amplification and sampling assemblies with fixed gains differing from one to another, an amplifier whose gain is able to take on several predetermined values, connection means for selectively connecting one of the assemblies to said amplifier, comparison means comparing the amplitude of the signals at the output of the amplifier with threshold voltages and a selection member for choosing the assembly and the gain of the amplifier as a function of the comparison. In each of the assemblies, the amplification function is provided either by amplifier stages and/or by sample and hold units.

What is claimed is: 
     
       1. In a device for amplifying and sampling high dynamic multiplexed signals so as to give the signals a desired amplitude before application thereof to an analog-digital converter, including amplification and sampling means applying several different amplification gains to each multiplexed signal, means for comparing the amplitude of the amplified signals with predetermined threshold voltages and means for selecting from the signals of different amplification gains that one whose gain gives the desired amplitude, said amplification and sampling means include three amplification and sampling assemblies whose fixed gains differ from one to another, a variable gain amplifier whose gain is able to take on several given values and connection means for selectively connecting one of the three amplification and sampling assemblies in series with said variable gain amplifier, the fixed gains of the three assemblies and the given values of the gain of the variable gain amplifier being chosen so that the overall gain applied to the multiplexed signals is one of the successive powers of an elementary gain value. 
     
     
       2. The device as claimed in claim 1, wherein the first amplification and sampling assembly includes a first sample and hold unit with a gain equal to unity, the second includes an amplification stage with fixed gain whose output is connected to the input of a second sample and hold unit and the third includes a third sample and hold unit adapted for communicating a predetermimed fixed amplification gain, the input of the third sample and hold unit being also connected to the output of said amplification stage. 
     
     
       3. The device as claimed in claim 1, wherein said first amplification and sampling assembly includes a first sample and hold unit with a gain equal to unity, the second, a second sample and hold unit adapted for amplifying with a predetermined fixed gain the signals which are applied thereto, the third, a third sample and hold unit also adapted for amplifying with a predetermined gain the signals which are applied thereto, the three sample and hold units being connected in series, the output of one being connected to the input of the next and their ouputs being connected respectively to said connection means. 
     
     
       4. The device as claimed in claim 1, wherein each of said three amplification and sampling assemblies includes an amplification stage with predetermined fixed gain and a sample and hold unit, the three amplification stages being interconnected in series, the output of one being connected to the input of the next and the three sample and hold units being respectively connected by their inputs to the outputs of the three amplification stages and by their outputs to said connection means. 
     
     
       5. The device as claimed in one of claims 1 to 4, wherein said elementary gain is chosen equal to two. 
     
     
       6. The device as claimed in claim 5, wherein the gains of said amplification stages or of the sample and hold units are equal either to unity, or to twice the maximum gain of said variable gain amplifier. 
     
     
       7. The device as claimed in claim 2, wherein the gain of said fixed gain amplification stage and that of the third sample and hold unit are both equal to twice the maximum gain of said variable gain amplifier. 
     
     
       8. The device as claimed in claim 3, wherein the gains of said second and third sample and hold units are both equal to twice the maximum gain of said variable gain amplifier. 
     
     
       9. The device as claimed in claim 4, wherein the gains of said second and third amplification stages of the series are both equal to twice the maximum gain of said variable gain amplifier. 
     
     
       10. The device as claimed in claim 1, wherein said comparison means include amplifiers for comparing the amplitude of the signal from said variable gain amplifier with two reference voltages.